1. Field of the Invention
This invention relates in general to well fracturing, and in particular to the use of capsules contained in a fluid and designed to implode at selected hydrostatic pressures in order to release acoustical energy waves in the fluid in a well bore to obtain fractures in the oil bearing formations.
2. Description of the Prior Art
The prior art broadly includes two well fracturing methods and apparatus utilized to obtain the fracturing of underground oil bearing formations.
One form of the prior art utilizes fluidic oscillators connected remotely if desired with the output of a fluid pump to generate pressure fluctuations that are acoustically coupled with a selected zone in a well bore. This concept is disclosed in a number of U.S. Patents issued to Albert G. Bodine, several of which are listed below.
______________________________________ 1. 2,680,485 Apparatus for Augmenting the Flow of Oil From Pumped Wells 2. 2,700,422 Sonic System for Augmenting the Extraction of Petroleum From Petroleum Bearing Strata 3. 2,871,943 Petroleum Well Treatment by High Power Acoustic Waves to Fracture the Producing Formation 4. 3,016,095 Sonic Apparatus for Fracturing Petroleum Formation 5. 3,322,196 Electro-Acoustic Transducer and Process for Using Same for Secondary Recovery of Petroleum From Wells 6. 3,578,081 Sonic Method and Apparatus for Augmenting the Flow of Oil From Oil Bearing Strata. ______________________________________
The above enumerated patents require the transmission of acoustical wave energy generally through a fluid medium to remote areas of the well in order to obtain the desired fracturing of the underground oil bearing formation.
The other form of system disclosed in the prior art employs well fracturing methods and apparatus whereby pressure fluctuations are generated in a well bore by pumping fluid through a first conduit to drive an acoustical oscillator coupled with an acoustical compliance that transmits the pressure fluctuations to a formation of the earth in a selected zone of the well bore. The well bore, which functions as a second conduit that contains the first conduit and the oscillator, returns fluid flow back toward a pump means. A variable restriction means such as a valve is used to adjust the back pressure in the well bore such that the maximum oscillated fluid pressure exceeds that pressure required for formation fracture. To achieve fracture only in the selected zone, acoustical isolation means are spaced above and below the acoustical oscillator to confine the pressure fluctuations to that zone. Also, the density of the fluid circulated in the well bore may be selectively varied to achieve fracture in the selected zone. This is illustrated in the patent listed below.
______________________________________ 7. 3,842,907 Acoustic Methods for Fracturing Selected Zones in a Well Bore ______________________________________